When should fluid boluses be given in cases of hypotension?

When to Give Fluid Boluses in Hypotension

Fluid boluses should be given in hypotension after assessing fluid responsiveness, with initial administration of 30 mL/kg crystalloid within the first 3 hours for septic shock, followed by additional fluids only if the patient demonstrates a positive response to fluid challenge. 1

Assessment of Fluid Responsiveness

• Perform a passive leg raise (PLR) test before administering fluid boluses to predict fluid responsiveness. An increase in cardiac output after PLR strongly predicts fluid responsiveness with high specificity (92%) 1
• Dynamic variables are preferred over static variables to predict fluid responsiveness when available 1
• No increase in cardiac output after PLR indicates patients who likely would not respond to fluid (88% sensitivity), suggesting the need for vasopressors rather than additional fluids 1
• Only about 50-60% of hypotensive patients respond to fluid boluses, making assessment of fluid responsiveness critical 1, 2

Indications for Fluid Boluses

Sepsis and Septic Shock

• Administer at least 30 mL/kg of IV crystalloid fluid within the first 3 hours for sepsis-induced hypoperfusion 1
• Septic shock is defined as systolic blood pressure <90 mmHg (or a fall in systolic BP >40 mmHg), or mean arterial pressure <65 mmHg after a crystalloid fluid challenge of 30 mL/kg body weight 3
• For maternal sepsis without shock, administer 1-2 L complete within 60-90 minutes; for septic shock, administer total 30 mL/kg within 3 hours 1

Perioperative Hypotension

• For postoperative hypotension with positive PLR test, intravenous fluid would be appropriate 1
• If PLR test does not correct hypotension, focus on vascular tone and chronotropy/inotropy with vasopressors 1

Pediatric Considerations

• In children with hypovolemic shock, initial resuscitation should begin with isotonic crystalloids or albumin, with boluses of up to 20 mL/kg over 5-10 minutes 1
• Titrate to reversing hypotension, increasing urine output, and attaining normal capillary refill, peripheral pulses and level of consciousness 1
• Stop fluid administration if hepatomegaly or rales develop, and initiate inotropic support instead 1

Fluid Bolus Administration Protocol

1. Initial Assessment:

   • Determine if hypotension is likely fluid-responsive using PLR test or dynamic parameters 1
   • Check for signs of fluid overload (pulmonary edema, hepatomegaly, rales) 1

2. Fluid Selection:

   • Use isotonic crystalloids (e.g., normal saline, lactated Ringer's) for initial resuscitation 1
   • For sepsis, use dextrose-containing solutions when administering vasopressors 4

3. Administration Rate:

   • For septic shock: 30 mL/kg within first 3 hours 1
   • For perioperative hypotension: 500 mL crystalloid bolus over 10-15 minutes 1
   • For pediatric patients: 20 mL/kg over 5-10 minutes 1

4. Reassessment:

   • After each bolus, reassess hemodynamic status through clinical examination and available physiologic variables 1
   • Look for improvement in blood pressure, heart rate, urine output, mental status, and peripheral perfusion 1

When to Stop Fluid Administration

• Stop fluid resuscitation when:
  • Blood pressure normalizes (target MAP ≥65 mmHg) 1
  • Signs of adequate tissue perfusion are present 1
  • Patient develops signs of fluid overload (pulmonary edema, hepatomegaly, rales) 1
  • Patient no longer demonstrates fluid responsiveness on reassessment 1

When to Switch to Vasopressors

• Initiate vasopressors if:
  • Hypotension persists after adequate fluid challenge (30 mL/kg) 3
  • Patient demonstrates negative response to PLR test 1
  • SBP remains <90 mmHg or MAP <65 mmHg despite fluid administration 1
  • Signs of fluid overload develop before achieving hemodynamic targets 1

Common Pitfalls and Caveats

• Fluid overload increases mortality, organ dysfunction, and ICU length of stay; avoid unnecessary positive fluid balance 2
• The PREPARE II trial showed that crystalloid fluid bolus alone failed to prevent cardiovascular collapse in critically ill patients undergoing rapid sequence intubation 1
• Recent evidence suggests that physiologically informed fluid and vasopressor resuscitation guided by PLR-induced stroke volume change may improve outcomes compared to usual care 5
• Only about 50-60% of hypotensive patients will respond to fluid boluses, making assessment of fluid responsiveness crucial 1, 2
• In patients with preexisting cardiac dysfunction, pulmonary hypertension, or risk of pulmonary edema, early use of vasopressors may be preferred over excessive fluid administration 1